Circadian-related Genes Research Articles

A pilot study for circadian gene disturbance in dementia patients

Disturbance of circadian gene regulation might contribute to behavioral and psychological symptoms in dementia patients. This study was to evaluate the CpG island methylation status on the circadian gene promoters in dementia patients. We conducted a set of methylation specific polymerase chain reaction (mPCR) followed by nucleotide sequencing to analyze the methylation status within the promoters of nine circadian-related genes, including PER1, PER2, PER3, CRY1, CRY2, CLOCK, BMAL1, TIM and CK1epsilon, in the genomic DNA from the peripheral blood leukocytes of 80 dementia patients and 80 age- and gender-matched controls. A total of seven dementia patients (7/80) had CpG island methylation in the circadian genes and none of the controls had methylation. There were three and four patients had CpG island methylation on the promoters of PER1 and CRY1, respectively. Dementia with Lewy body (DLB) patients had the significantly highest frequency of circadian gene CpG island methylation (35.7%). It suggested that epigenetic methylation of circadian gene was more prevalent in dementia patients, especially for the DLB patients. The significance of circadian gene methylation in clinical behavior/sleep disturbance in dementia patients needs further study.

Altered Circadian and Homeostatic Sleep Regulation in Prokineticin 2-Deficient Mice

Sleep is regulated by circadian and homeostatic processes. Recent studies with mutant mice have indicated that circadian-related genes regulate sleep amount, as well as the timing of sleep. Thus a direct link between circadian and homeostatic regulation of sleep may exist, at least at the molecular level. Prokineticin 2 (PK2), which oscillates daily with high amplitude in the suprachiasmatic nuclei (SCN), has been postulated to be an SCN output molecule. In particular, mice lacking the PK2 gene (PK2-/-) have been shown to display significantly reduced rhythmicity for a variety of circadian physiological and behavioral parameters. We investigated the role of PK2 in sleep regulation. EEG/EMG sleep-wake patterns were recorded in PK2-/- mice and their wild-type littermate controls under baseline and challenged conditions. PK2-/- mice exhibited reduced total sleep time under entrained light-dark and constant darkness conditions. The reduced sleep time in PK2-/- mice occurred predominantly during the light period and was entirely due to a decrease in non-rapid eye movement (NREM) sleep time. However, PK2-/- mice showed increased rapid eye movement (REM) sleep time in both light and dark periods. After sleep deprivation, compensatory rebound in NREM sleep, REM sleep, and EEG delta power was attenuated in PK2-/- mice. In addition, PK2-/- mice had an impaired response to sleep disturbance caused by cage change in the light phase. These results indicate that PK2 plays roles in both circadian and homeostatic regulation of sleep. PK2 may also be involved in maintaining the awake state in the presence of behavioral challenges.

Phase analysis of circadian-related genes in two tissues.

BackgroundRecent circadian clock studies using gene expression microarray in two different tissues of mouse have revealed not all circadian-related genes are synchronized in phase or peak expression times across tissues in vivo. Instead, some circadian-related genes may be delayed by 4–8 hrs in peak expression in one tissue relative to the other. These interesting biological observations prompt a statistical question regarding how to distinguish the synchronized genes from genes that are systematically lagged in phase/peak expression time across two tissues.ResultsWe propose a set of techniques from circular statistics to analyze phase angles of circadian-related genes in two tissues. We first estimate the phases of a cycling gene separately in each tissue, which are then used to estimate the paired angular difference of the phase angles of the gene in the two tissues. These differences are modeled as a mixture of two von Mises distributions which enables us to cluster genes into two groups; one group having synchronized transcripts with the same phase in the two tissues, the other containing transcripts with a discrepancy in phase between the two tissues. For each cluster of genes we assess the association of phases across the tissue types using circular-circular regression. We also develop a bootstrap methodology based on a circular-circular regression model to evaluate the improvement in fit provided by allowing two components versus a one-component von-Mises model.ConclusionWe applied our proposed methodologies to the circadian-related genes common to heart and liver tissues in Storch et al. [2], and found that an estimated 80% of circadian-related transcripts common to heart and liver tissues were synchronized in phase, and the other 20% of transcripts were lagged about 8 hours in liver relative to heart. The bootstrap p-value for being one cluster is 0.063, which suggests the possibility of two clusters. Our methodologies can be extended to analyze peak expression times of circadian-related genes across more than two tissues, for example, kidney, heart, liver, and the suprachiasmatic nuclei (SCN) of the hypothalamus.

Two pedigrees of familial advanced sleep phase syndrome in Japan.

To determine whether a known missense mutation (bp2106 A/G) in hPer2 (a human homolog of the Drosophila period gene) for familial advanced sleep phase syndrome in a Caucasian family is involved in Japanese familial advanced sleep phase syndrome pedigrees. We identified 2 new Japanese families with advanced sleep phase syndrome, and a systematic survey was carried out in 28 relatives of theses 2 families. A total of 9 affected subjects were identified. The affected members showed significantly strong morningness tendencies compared with the unaffected members in various circadian parameters including the Horne-Ostberg Morningness-Eveningness Questionnaire score (77.3 +/- 4.8 vs 57.5 +/- 7.6, p < 0.001), average sleep-onset time (20:45 +/- 75 min vs 23:16 +/- 64 min, p < 0.02), and average wake time (4:55 +/- 38 min vs 6:13 +/- 25 min, p < 0.01), as well as saliva dim-light melatonin-onset time (20:15 +/- 21 min vs 22:25 +/- 65 min, p < 0.02). DNA samples were obtained from 7 affected and 7 unaffected subjects. None of the tested subjects possessed the missense mutation (bp2106 A/G) in hPer2. Furthermore, there is no significant linkage between affected subjects with hPer2 region by 2-point mapping and by direct sequencing of 23 exons of hPer2. These findings support the notion of genetic heterogeneity of familial advanced sleep phase syndrome cases in humans. The search for more familial advanced sleep phase syndrome cases and for loci other than hPer2 are necessary to further examine the roles of circadian-related genes in genetically determined human circadian rhythm disorders.

Intracellular calcium mobilization induces period genes via MAP kinase pathways in NIH3T3 cells

Mammalian period genes have a pivotal role in generating circadian rhythms and are rapidly induced by several stimuli in mammalian cells. In the present study, we revealed that treatment with thapsigargin significantly induced transcripts of mouse period 1 and 2 ( mPer1 and mPer2) but not mPer3 among circadian related genes in NIH3T3 cells. Thapsigargin-induced mPer1 and mPer2 mRNA expressions took distinct signaling pathways from protein kinase C and cAMP, but were partially inhibited by inhibitors of MEK1 and p38 mitogen-activated protein kinase, respectively. Thus, the present study suggested that intracellular calcium is one of multiple signaling stimuli triggering mPer gene expression in NIH3T3 cells.